“There is a great article in the McKinsey Quarterly on cheerfulness. (You may have to register with them to see the article but it is worth it.)
They have done studies using Britain’s Royal Navy (of all places) on the effect that cheerfulness has on employees. ” … naval training is predicated on the notion that when two groups with equal resources attempt the same thing, the successful group will be the one whose leaders better understand how to use the softer skills to maintain effort and motivate. For officers leading small teams in constrained quarters, there’s no substitute for cheerfulness and effective storytelling.”
“No one follows a pessimist, and cheerfulness is a choice. It has long been understood to influence happiness at work and therefore productivity. The cheerful leader in any environment broadcasts confidence and capability, and the Royal Navy instinctively understands this. It is the captain, invariably, who sets the mood of a vessel; a gloomy captain means a gloomy ship. And mood travels fast.”